The present disclosure relates to the processing of substrates in plasma process equipment. In particular, it provides a method to achieve conformal selective etching.
The use of plasma systems for the processing of substrates has long been known. For example, plasma etch processing of semiconductor wafers is well known. Historically, plasma etching systems have been utilized to provide selective anisotropic etching techniques. A number of new complex substrate integration schemes have been developed. Some of these schemes require etch processes that are both selective to layers not being etched and that provide conformal (or isotropic) etch characteristics. More particularly, some of these schemes require conformal etching of silicon nitride while providing selectivity to exposed silicon or silicon oxide layers. Specifically, silicon nitride etch plays a key role in a number of these schemes, including hard mask processes and spacer applications. For example, a variety of critical process flows may require trimming silicon nitride hard masks, trimming silicon nitride spacers, removing silicon nitride spaces, revealing structures underneath silicon nitride spacers, fin reveal, inner spacer etching, etc. However, most plasma chemistries that are capable of etching silicon nitride also etch common materials often exposed in such processes, such as, for example, silicon or silicon oxide layers and most plasma chemistries provide for anisotropic etching as opposed to conformal (isotropic) etching.
It would be desirable to provide a plasma process that provides conformal etching of silicon nitride while providing selective etching of the silicon nitride to other layers, such as for example, silicon or silicon oxide layers.